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Geologic maps serve as a valuable tool in resource exploration.Traditional mapping is characterized by time-intensive and high-cost fieldwork, but through multispectral and hyperspectral remotely sensed images it is possible to map extensive areas instantly.
Geologic background of Marysvale volcanics
Background
FWHM
Full Width Half Mass (FWHM) is an important concept for understanding how different band values are calculated.
Bandpass filters are used to isolate specific wavelengths. The graph below visualizes the idea of FWHM. Each band in a spectral device only takes in a specific range of wavelengths, often the wavelength for each band is just denoted as the peak, but in reality each sensor is collecting a range of wavelengths. This is determined by denoting the FWHM as the area between the 50% transmittance on either side of the curve.
In this plot you can see all the bands for Landsat 8, Hyperion, and ASTER. With their FWHM denoted as boxes. Its important to point out how Landsat 8 does have a band in the Short Wave Infrared (SWIR), but the FWHM is wide and this means that any SWIR data saved for this band could be attributed to any wavelength inside of the FWHM.
Landsat
Landsat is an ongoing satellite imagery collection system with a recurrence interval of 8 days. Now lets make some plots of different mineral groups:
To create a map of Iron Oxides with Landsat 8 imagery, you will need to perform bandmath. This image was created using Band4/Band2
Hydroxyl mineral mapping can be created using Band6/Band7
Ferrous (iron minerals) can be mapped using Band6/Band5
A Sabins Ratio plot can be created by combining these three plots into an RGB profile. This leaves colors show a few different things - -
ASTER
